It's a Real Force, this Centrifugal Thing.
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Matt Bryda
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Yes and Let's figure out how to look at it and maybe control it to our advantage.
Hello mr. ball, said mr. clubface, wham!!!!
I wish I could have more to add to this discussion. I feel like something great is going to happen soon in this thread.
Matt
JThompson
New
I'm not sure what car tires have to do with this. Isn't friction what keeps the car from swinging off the road, the same way the pressure on the grip of the club keep the club from flying from the hands? What happens on icy roads?
Yes, friction is what keeps a car from swinging off the road. Friction is a force. Lets take the example of a car driving around a turn. Centrifigal force exist because objects that are in motion want to remain in that motion unless an equal or opposite force acts upon it. In a perfect world, if I am driving a car in a straight line and take my foot off the accelerator and coast. The car will remain at that speed forever. (unless another force acts upon it) It wants to remain at that speed. If I turn the wheel, the friction of the tires has acted upon the momemtum of the car and created both centripital and centrifugal force. The constant "need" for the car to want to stay in a straight line (the mometum) is considered centrifigal force. The force that is preventing the car from going in the straight line is centripital force. If the car's tires (centripital force) ever offer less force then the amount of centrifigal force (icy roads) the car will continue straight (bam).
The same principles are applied to the golf swing.
The debate lies in what action "mostly" causes the clubhead to rotate and accelerate as much as it does. But however fast the club travels it will create both centripital and centrifigal force. For ANY object to move in a circlular patern it MUST have both.
ZAP
New
Eyeoffish,
Sorry. I think you're way off base.
-1- My point is concerning centrifugal force not centripetal force.
-2- Also not about release of the club but solely if centrifugal force is real or not.
-3- Fictitious: unreal - lacking in reality or substance or genuineness.
You have made my point exactly. It seemed to me that you were debating one thing and Brian was debating another topic all together. The two forces have to be related in some way correct? But the real question for a golf forum is not whether they exist but simply if we can use either or both to improve our golf games or our teaching. The fact that the club is moving in an arc of some sort makes it mandatory that there will be forces involved to steer it along that path.
mandrin
New
Brian,
You mention,
-1- The pivot's internal rotation, and
-2- The golfer pulling upwards on the grip.
And you feel that -2- is more important than -1-.
I am guessing as to what you are trying to say but from your enthusiastic reaction to another post I am inclined to think that you mean that the angular motion of the club is primarily determined by the linear force exerted on the grip end. However this is still mainly due to the pivot's internal rotation.
But I like to remind that the initial point I made is simply to clarify your remark about centrifugal force being a fictitious force. If you feel that it is actually a real force than we are hence on the same wavelength.
Hey Mandrin, have you checked out the wikipedia entry for "Centrifugal force" ?
Centrifugal force - Wikipedia, the free encyclopedia
Centrifugal force - Wikipedia, the free encyclopedia
BTW...most 10 year olds pretty familiar with this??
LOL you'd be surprised.10 year olds are pretty savvy these days.It was in the news a while back concerning the 6 billion dollar Large Hadron Collider,otherwise I wouldn't have had a clue about it.
mandrin
New
Mike,
I have tried to answer in way which might be more attractive considering your acknowledged preference of logic over science.
If you try to understand the why of it all you will be going nowhere. If your aim is to know how things relate and operate than we are talking business. Inertia, it is because it is, there is no explanation. If someone has one he will be assured to be the next candidate for a Noble prize in physics.
Arestotle's physics dominated and smothered scientific thinking for almost 2000 years and finally slowly by contributions by various scientists such as Copernicus, Descartes, but especially by Galileo, things evolved and culminated with Newton's efforts. One of the main issues was indeed coming to grasp with concepts such as inertia, straight line and circular planetary motion. Eventually Newton finally embraced it all in one genius sweep. But there are still question marks.
Let me just quote a bit from 'Analytical Mechanics' by Fowles / Cassiday.
Newton's laws of motion can be thought of as a prescription for calculating the subsequent motion of a particle or a system of particles given a knowledge of its position and velocity at some instant in time. These laws, in and out of themselves say nothing about the reason why a given physical system behaves the way it does. He refused to speculate why objects move the way they do. Whatever “mechanism” lay behind the workings of physical systems remained forever hidden from Newton's eyes. He simply stated that, for whatever reason, this is the way things work as demonstrated by the power of his calculational prescription to predict, with astonishing accuracy, the evolution of physical systems, set in motion. Much has been learned since the time of newton. But the basic fact of physical law persists. The laws of motion are simply prescription. They tell us how things work – not why.
And some more from 'Physics' by Resnick / Halliday.
There are still other serious questions of logic which can be raised in regard to Newton's laws. Do these laws define the concepts of force so that they are not laws at all but just definitions? And if so, what makes this definition “useful” ? Or is force defined in another way so that F=ma is really a law connecting quantities previously defined? And if so, what general significance do we give to the concept of “force”? There is no way to make Newton's laws (in the conventional form) rigorous and logical by any simple twisting of words or special interpretation.
Mike don't look upon science for being able to give you a fundamental understanding. You are much better off considering science as a sophisticated cookbook revealing the fascinating magic of our environment through rules and laws obtained from patient and long-standing observations. That reality can be fitted somehow and somewhat into mathematics is indeed hovering on magic, at least that is the way I feel it.
So let's just be very down to earth and pragmatic.
If something can be measured we assume that it exists.
Centrifugal force can be readily measured hence it exists.
What else is there to say?
It is therefore it is.
With regard to the more technical aspects of your questions. Some darned good thinking going on. Virtually all references to centrifugal forces in science books/articles are done using the example of a simple particle whirling around a fixed center. Hence as a consequence virtually all discussions on golf forums or elsewhere are based on this simple example. A gross over simplification of real situations which are normally much more complex.
It is indeed obvious that a golfer/club ensemble is not just a simple particle whirling around a fixed center. The golf club has an complicated kinetic interaction with the arms and the rest of the golfer and its center of rotation is not fixed in space. Hence your questioning is indeed very valid. It is for me the first time I see someone raising these points. Where exactly is the instantaneous center of rotation of the clubhead ? Is it located at the wrist joint or somewhere else in space? Are the centripetal/centrifugal force vectors indeed aligned with the shaft or not?
Mike, I will these questions for incubation for now. I don't want to race ahead of myself. I will post it all eventually.
Steve Greffen
New
Hah hah! I had to Google it to find out what you were talking about.
mandrin
New
greenfree,
The confusion started likely right from the beginning with Newton himself as he used centrifugal force to mean different things depending on context. However initially centrifugal force meant basically the counterpart of centripetal force as immediately follows from Newton's third law.
Then came around the concept of non-inertial reference frames, a mathematical concept to simplify calculations, and fictitious forces had to be introduced to make Newtonian mechanics valid in these frames. One of these pseudo forces introduced is the infamous fictitious centrifugal force.
Scientists, pseudo scientists and teachers seemingly are frequently in love with non inertial reference frames, even if few are actually using them. And, likely for this reason, as time went by, the original meaning of centrifugal force was forgotten somehow and centrifugal force started to be referred to in general as a fictitious force.
There is another use of centrifugal force which comes about specifically in multi body dynamics where scientists use normally generalized coordinates. But this particular specialized use is not contributing to the existing confusing.
In science textbooks one explains rotation of objects in an overly simplistic way by analyzing it usually as a simple mass whirling, with constant speed, around a fixed center. However in real life things are way more complex. In general as soon as there is any deviation of any moving object from a straight line there are centripetal/centrifugal type forces coming into play relative to the instantaneous center of rotation.
It is also possible to argue that scientists are so used to look for causes that they probably have developed a neglecting attitude towards effects/reactions. Centrifugal force is a reaction force whereas centripetal force is an action force. However action and reaction are so closely knitted that it is difficult to really see them as being very different and having an unequal status. If you were hit by a falling rock I am sure that the serious wound inflicted onto your skull will forever change your mind about inertia reaction forces frequently being often referred to nonchalantly as being fictitious, pseudo or similar type of epithets.
Another reason for the existing confusion is the fact that when deriving the governing equations for rotating objects in an inertial reference frame, reaction forces such as centrifugal forces don't appear explicitly into these equations. Since they don't appear in these equations some scientists act, as a consequence, as if they don't exist as real forces. For instance, some while ago, nmgolfer, in an attempt to prove me wrong proceeded exactly with this erroneous exercise. Some with their nose to close to mathematics seem to forget reality.
There is also another indeed very common approach to centrifugal force, which is not correct either, where one represents centrifugal force as the inertial tendency for a particle to continue moving away from the axis of rotation. Wrong for two basic reasons – tendency is not a force but an abstract notion which can't be measured. A force either is a force or it is not. Moreover this approach violates Newton's third law. Force never exists in isolation but always exists as an opposing action reaction pair.
Another fact indirectly helping maintaining confusion is that rotation is rather counter intuitive. In rotation one has a force which is not in line with the motion but rather perpendicular to it. We are so used to pulling and pushing where force and motion are aligned that it is not easy to fathom for a circular motion there to be, for a seemingly peaceful 'stationary' looking rotation, very large centripetal/centrifugal forces at work.
There are also those who maintain that centrifugal force does not exist but than immediately continue saying that it is very convenient to use it as if it really existed. And so the confusion continues. Example: I remember reading posts where it was mentioned that Homer Kelley was quite aware that, scientifically, centrifugal force did not really exist but that he used it to keep close to well entrenched popular concepts.
The information below posted on a TGM forum seems to reinforce this notion:
Homer Kelley was well aware of the academic arguments concerning centrifugal force. In fact, he discussed those issues with our January 1982 GSEM class. In one of the lighter-hearted moments of that week, and with his voice mocking his detractors, he said: "There is no such thing as centrifugal force, son!"
It is indeed rather funny that centrifugal force, seemingly acknowledged as not existing, is nevertheless deemed to be worthy to constitute one of the corner stones of the golfing philosophy exposed in The Golfing Machine.
I believe gravity has been described as fictitious also.It also defies Newtons laws.Jump of a building and you will accelerate towards the ground.Nothing had pushed or acted on you yet you are hurled towards the ground.Einsteins general relativity theory is the best explanation yet but even that theory does not explain other phenomenons.
There are many things we don't know anything about yet so it's best to keep an open mind.The large hadron collider might answer a few of those questions.
I'm not a scientist per say, just smart enough to understand some of the concepts. To me the swing force comes mainly from centrifugal force because you also experience the "shaft droop" that was discussed in another topic. Either way, to the golfer and instructor, it's speed that is generated. I would say that centrifugal force is created more by an active pivot but with many golfers that force is not enough. Many add some push to the club to increase that speed if they aren't generating enough speed in a pivot. I just try to look at it from a perspective of what I can do as a golfer and not care so much about the specific scientific principles involved.
mandrin
New
savydan,
The exact formulation for the centrifugal/centripetal forces, using a double or triple pendulum model, is quite complicated but it is possible to get a rather good idea with a simple common sense approach.
We assume that the hands are virtually stationary at impact allowing to take the wrists joints as the instantaneous center of rotation of the club.
At impact the lead arm and club are almost in line therefore at that time the centrifugal pull due to rotation of the clubhead is directly transmitted to the lead shoulder socket.
The rotating lead arm itself is also causing some centrifugal pull on the shoulder socket but it is substantially less than that exerted by the fast moving clubhead.
All we have to do now is the use the simple centripetal force expression for a point mass rotating about a fixed center ...... M v^2 /R.
M is the mass of the clubhead
v is the linear speed just prior to impact, and,
R is distance approximately from sweet spot to wrists.
A good pro swing attains a clubhead speed with driver of about 190 km/hr.
Clubhead mass about 0.2 kg.
R about 1.10 m.
Substituting gives about 506 N (114 lbs) for the centrifugal pull on the lead shoulder socket.
As you can see the centrifugal pull is very large but it lasts for a very short interval of time and indeed surprisingly.... reaction time.... we usually hardly notice it.
In the long run however, glove/hand will show definitely clear evidence of this force.
Think of Moe Norman who practiced till hands were bleeding.
Taking now your 5 iron example....
M assumed about .3 kg
Assuming v about 145 km/h
R about 1.05 m
The centrifugal pull caused by clubhead is than approximately 464 N (104 lbs)
To summarize, above constitutes a simple but fair approximation for centrifugal pull when only clubhead itself is considered. It concerns the maximum centrifugal force which exists for a small fleeting moment when arm and shaft are virtually in line just before impact. For the total centrifugal pull exerted on the lead shoulder joint one has to consider a small additional contribution by both shaft and lead arm.
Also it is a fair approach for someone letting the club rather freewheel though impact. However for a hacker, with a rather low clubhead speed, and really trying to muscle the clubhead through impact the ball, it is not. The instantaneous center of rotation for the club head is than moving towards the lead arm shoulder joint.
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Jared Willerson
Super Moderator
I appreciate your thoughtfulness good sir. It is admirable the amount of time you put in to constructing posts and adding to the body of knowledge here. Thank you.
I thought it would be a significant force/weight, but I didn't think it would be over 100lbs. Pretty interesting information.
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